Low aromatic hydrocarbon fluids, i.e. typically containing less than 1 wt % total aromatics, are used in a diverse range of applications where chemical inertness, thermal/oxidative stability, low toxicity, and low odor are desired. These hydrocarbons are characterized by their paraffinic nature, a carbon number distribution in the C5-C40 range, preferably in the C15-C40 range. For most applications, the preferred fluids have a flash point greater than about 100° C. Other properties specified for hydrocarbon fluids include viscosity (specification range dictated by application), and pour point (typically <−10° C.). Mineral oil is an example of a low aromatic hydrocarbon fluid.
As a result of a number of industry trends, such as increased demand for drilling and hydraulic fracturing fluids and tightening environmental standards concerning eco-toxicity, biodegradability, and work place safety/health, demand for such paraffinic fluids has experienced rapid growth. This has coincided with an increased demand for middle distillate fuels (C10-C20 hydrocarbons) that compete for much of the same petroleum molecules. Furthermore, with high aromatic feeds such as tar sands finding their way into the North American petroleum pool, more extensive upgrading (such as aromatic hydrogenation) is required in order to meet fluid product specifications. Use of mineral oils in cosmetics and food preparation is banned in the European Union due to concerns about presence of trace amounts of carcinogenic polyaromatic hydrocarbons—thus providing the need for synthetic products that are inherently free of these aromatic components.
Synthetic hydrocarbon products have been used for some industrial fluid applications. For example C16/C18 linear alpha olefins (LAOS) from oligomerization of ethylene, are used as drilling base fluids. However, this synthetic route is non-selective, producing a wide distribution of even carbon number LAOS, mostly in the C4 to C10 range, such that further expensive processing and separation steps are required to achieve the desired LAO product. Moreover, these even carbon number LAOs in the C4 to C10 range are chemical intermediates and not end-products suitable for use in industrial fluid applications.
Use of the Fischer-Tropsch process for producing synthetic hydrocarbons suitable for certain hydrocarbon fluid applications has also been reported. However, the FT process is very capital intensive and most of the FT manufacturing is dedicated to fuel production. Because the hydrocarbon range of interest for synthetic hydrocarbon fluids comprises a small percentage of the wide distribution of FT hydrocarbons (C1-C50+), it is more economical to hydrocrack and hydrotreat the FT wax and light oil fractions into complex compositions for fuel use.
There is thus a need for new processes for producing hydrocarbon fluids from alternative feeds. More specifically, there is a need for hydrocarbon fluid products that, based on their feedstocks and conversion processes, are substantially free of aromatics without further processing such as by aromatic hydrogenation conditions.